Power unit



1942- A. M. MiCHELL 2,269,281

' POWER UNIT Filed April 26, 1938 3 Sheets-Sheet l Jan. 6, 1942- A. G. M. MICHELL POWER- UNIT Filed April 26, 1958 s Sheets-Sheef 2 WWWM 3, WW

.Jah. 6, 1942.

A. ca. M. MICHELL POWER UNIT Filgd April 26, '1938 -5 Sheets-Sheet 5 Patented Jan. 6, 1942 A O-FF1 POWERUNIT Anthony Georg e Maldon Michell, Melbourne, Victoria, Australia v Application April 26, 1938, Serial o. '204,4(l3

5. Claims.

' arranged parallel to the power shaft actuated by said pistons.

A main purpose of the inventionisthe, production of power units of the least possible. bulk and weight relatively to their power, it being known from theroetical considerationsand confirmed by experience in the art that subdivision of the essential organs (e, g. cylinders), ofan engine into a plurality of smaller organs having the same total output tends-to reduction, of total weight. Likewise, a composite engine, comprising a plurality of component engines coupled together, will be lighter than a similar singleengine of the same power.

A power unit consisting of component. engines combined according to the invention presents also the advantage that one .or more of the com- .ponents may be detached,'or,allowed to remain idle, for purposes of inspection,adjustment, or repair, or to economize fueLwhile the remaining components continue to be effective .for supplying power to the common power take-off. I

A further purpose and advantage of the construction is that the powertake- 1f of the unit may have any desired ratio of rotative speed relatively to the frequency of reciprocation of the pistons of the component engines (such ratio being arranged in the gearing essential to the construction of the combined unit), whereby in most cases the use of any gearing between the powertake-off of the prime-mover and the driven machine can be avoided.

Having these characteristics, prime-movers constructed according to the invention are specially applicable to. the, propulsion of aircraft.

In a particularapplication of the invention by means of component engines of the opposed-piston crankless type, as described in the following specification, each engine is constructed with two engine shafts in longitudinal alignment with each otherieach of the shaftsbeingseparately geared to the common power shaft of the composite unit), instead of having only a single power-shaft. asv hitherto. ,An engine so constructed is the subject of an application divisional Fig. v1 is a longitudinal section on the broken line I, l i-Fig. g, of a. powerunit constructed according tofthe invention.

Fig. 2 (which shows only the moving parts of the unit) is a cross-section'on the line 2, 2 of Figyl. I r

These views are to some extent diagrammatic, serving to illustratebroadly the principle of the invention. p I a Fig. 3 is a half cross-section of a component .engine showing details differing in some respects from those indicated in Figs. 1 and 2, and to a largerscalag Fig. 4 is a longitudinal :View of a complete power-unit, being partly ,in section and partly in external elevation, .and illustrates the ,application in the .invention .of crankless engines of the opposed-piston type.

Fig. 5 is, a half cross section, with details simplified for the. sake of \clearness, taken on thejlin 5, 5 ofFig. 4. J

The same reference numeral is applied to designate the same part wherever shown in the various figures. v s v I As shown in Figs. 1 and 2 each of the six com ponent crankless' engines of the, power unit comprises an engine-shaft .l l on which ,is mounted a slant, swash-plate or wobble plate, l2, caused to rotate with the Shaft H by the action of the pistons 13 reciprocating in the acylindersit. 'In the preferredconstruction shown, which is not however essential to the invention, the pi'stons w drive the' shaft l,| throughthe medium of a pair ofbearing slippers 15 mounted in the crosshead l5 which is rigidly attached to the piston by means of the piston rod I l. The shaft H and plate l2 are supported, against the .axialthrust exerted by the piston l3 :by means of the thrust bearing Iii. The shaft II is also supported in 'j ournal bearings 20,2041,

As shown in Figs. 1, and 2 each component, engine hasthree pistons l3, reciprocating three cylinders I 4, and the, complete power unit consists of six of such enginesarranged aboutv the common centre-line C, which is the .axisof the power take-oifiqf the ,unit. Any otherdesired numbers of component engines, and of cylinderrotating with their respective shafts ll and engaging with a main gear wheel 2.4 mounted .on

the stub shaft 2|. In the application of the invention to the power units of air-craft the aeropropeller may be mounted on the extension 25 of the stub-shaft 2|, and (the hollow extension 25 being arranged to extend through the boss of the propeller), a gun, (not shown), may be located wholly or partially within the space 23 enclosed by the component engines so. as to be adapted to fire through the hollow shaft 2| and propeller boss.

Any usual form of gearing or power-transmission (mechanical, hydraulic or electric) may be used for gearing the engine-shafts I I to the power take-off 2 I, alternatively to the gear transmission shown.

The moving parts of the composite unit may be contained and supported in common in a single casing, but preferably, as shown in Fig. 3, each component engine, comprising all the moving parts shown in Fig. 2 together with thrust and journal bearings as I8, 20, and 20a, is constructed as a self-contained unit having a separate frame. In the half-section, Fig. 3, the frames 3|, 3Ia, 3 lb of three of such engines are shown arranged in a semi-circle around the axis C, such frames being adapted to be bolted to the other frames forming-the composite unit, on radial planes indicated by the lines CA, CB, CC, CD, the external portions of the frames 3|, including the cylinders, forming a complete external covering throughout their length for the composite unit including the power take-off shaft 2|. The enclosure of the composite power unit is completed by end-casings, as 34 Fig. 1.

In the application of the invention to compression-ignition engines, shown in Figs. 4 and 5, each of the component engines (as shown in the upper portion of Fig. 4, which is a longitudinal section on the line 4, 4 of Fig. 5), comprises two engine shafts II, Ila, and a plurality of cylinders l4, each containing two pistons I3, I3a, respectively engaging with the two swash plates or slants I2, I2a (severally mounted on the shafts II, Ila), by means of the slipper bearings I5,- I 511 mounted in the cross-heads I6, I6a, as already described in connection with Figs. 1 and 2. The term slants will be used hereinafter to designate members I2, (2a. The shafts II, II a are respectively geared, as by'pairs of gear-wheels 23, 24 and 23a, 24a,

to the power take-off shaft 2| of the composite unit, so as to be caused to rotate-at equal speeds and in fixed angular relation to each other. The slants I2, I2a are thus caused to rotate in fixed,

and approximately opposite, mutual phase relationship, and the pistons I3, I3a to reciprocate in approximately opposite phases.

Individual frames 3I, 3Ia, etc., compr1sing the cylinders may be provided for the several engines as shown, these frames being bolted or otherwise attached together throughout their lengths and enclosing the power take-off shaft as already described in connection with Fig. 3.

Each component engine is thus amodified form splines 62.

of the opposed-piston internal-combustion engine described in .United States patent of Reissue -No. 17,273. While it has hitherto been the practice in the construction of engines of this type to mount the two slants rigidly upon a common shaft, whereby they were necessarily in. fixed 3 phase relation with each other, the-same fixed relationship of phase is secured-according to the present invention by the gearing of the two separately mounted shafts I I, II a, to the power take-off shaft 2|, of the composite unit.

The fuel injectors, especially those of the inner cylinders of the unit, are conveniently inserted into their combustion spaces between the adjacent ends of the two shafts II, Ila, with their axes on radial lines intersecting the common axis of the shafts, a so-called long-reach injector being suitable for the purpose. The injectors 36a (see Fig. 5) of the outer cylinders of the unit may of course be of the usual short type fitted in the usual way. The openings for the insertion of both classes of injectors are shown at 31, 31a in the lower portion of Fig. 4 (external view).

In the same figure are shown the external openings 4| for discharge of the exhaust gases from the exhaust chambers 42, and openings 43 for intake of scavenge air into the scavenge chambers 44. The cylinders communicate with the chambers 42 and 44 respectively through exhaust ports 45 and scavenge ports 46, arranged peripherally around each of the cylinders in the manner usual in engines of the opposed-piston type. The scavenge air may be supplied by a fan 5|, preferably gear driven from the shafts Ila, the delivery ports 52 of the fan-casing 53 being connected to the intake openings 43 by suitable conduits or casings not shown. The exhaust chambers 42,- and scavenge chambers 44 may be common to the whole power unit, or alternatively separate exhaust chambers and scavenge chambers, with separate exhaust and scavenge openings, may be provided for each engine.

It is to be understood that the mode of ar rangement of the scavenge and exhaust chambers and ports which is described in the preceding paragraph is applicable not only to the form of construction of the individual engines with paired shafts as shown in Figs. 4 and 5, but also to forms of construction in which each engine has only a single shaft.

The other usual accessories of internal-combustion engines such as fuel-pump 54, circulating water-pump 55, necessary lubricating and starting mechanisms, and the like, are preferably coupled, either directly or through gearing. to the shaft 2| of the combined unit.

The gearing by which each of the engine shafts II, II a, transmits power to the common power take-off, is preferably so arranged that each engine shaft can be readily disconnected from the transmission, and thereby detached, or allowed to remain. idle while other units continue to be effective for supplying power. An example of such an arrangement is shown in connection with the shaft II in Fig. 4. As shown in this figure, the thrust bearing I8 and outer bearing 2|! of the engine shaft II are supported in a spider 6| attached to the engine frame 3|. The portion of the shaft II extending beyond the bearing 20 is formed with splines 62. In the end-casing 34 of the power-unit is fixed a shaft 63. The sleeve 64 is rotatably supported at its outer end on the shaft 63, and at its inner end fits upon the shaft II and slidably engages the The gear wheel 23 is mounted by means of a feather or splines upon the sleeve 64 so as to be slidable thereon, and the sleeve is formed with a circumferential groove 65, adapted to be engaged by a collar and lever (not shown) so as to be readily moved in the axial direction at will. 7

It will be understood that when the sleeve 64 stands in engagement with the splines 62 of the shaft I I, as shown by full lines in the figure, the sleeve and gear wheel are compelled to rotate with the saft II which is then enabled to transmit power to the shaft 2|. When, on the other hand, the sleeve 64 is moved axially by means of its collar to the position shown by dotted lines, its inner end is detached from the shaft l l which is thereby rendered idle. The sleeve 64 then continues to run upon the shaft 63 being driven by the engagement of gear 23 to the main gearwheel 24 of the power unit.

The mutually-engaging splines of the shaft l I and sleeve 64 are so formed that the shaft and sleeve can only be put into engagement in one angular position, thus ensuring that the correct phase relationship of the shafts H and Ila. is maintained whenever the engine is put into operation.

Similar means of disengagement being prov vided for the shaft I la, as shown, and enginecasing 3|, Fig. 4, being constructed as a selfcontained section attached to the casings of the other engines of the power unit, as explained in connection with Fig. 3, it will be understood that effecting the disengagement of both shafts and disconnecting the casing 3| from the end casings 34 the component engine comprising all the moving parts and the casings 3|, spiders 6| and bearings may be removed without affecting the combination of the remainder of the power unit. Alternatively the engine may be left in position, and allowed to remain idle while the remainder of the composite unit continues to be operative.

By the provision (e. g. in air-craft and highpowered boats) of such facilities for the removal, or laying-off, of the component engines, the invention provides in a single composite power unit a degree of reliability which can only be secured otherwise by the installation of a multiplicity of separate power units. The latter arrangement involves of course the use of several of such separate engines to enable any one of them to be laid off without serious diminution of the available power. Also the locationof a multiplicity of engines in most cases presents considerable difiiculty and inconvenience. Moreover their supports and enclosures necessarily add to the total weight of the craft.

The construction which is the subject of the present invention enables all the principal advantages of subdivision of a power-plant to be secured, together with the evident convenience of centralizing the plant, and with a great diminution of the necessary weight.

It will be evident from the drawings, and more especially from Fig. 5, that the total sectional area of the cylinders of a composite engine constructed according to the invention, bears a much larger ratio to the total cross-sectional area of the power-plant, than is the case in the usual modes of construction. Since the total sectional area of the cylinders is an approximate measure of the power of an engine, it is apparent that a large saving of bulk relatively to power will be eflected by the application of the invention.

In the arrangement of the gearing of composite power units as hereinbefore described, the

gearing is preferably so arranged that no two engine cylinders in the whole unit are in the same phase of their cycles. The stresses imposed on the common power take-off elements arethereby minimized, and furthermore the number of torque impulses exerted by the unit is thereby increased to the maximum possible, whereby smooth operation of the unit is assured.

Although certain specific embodiments of the invention have been particularly shown and described it will be understood that it may be modified in various other ways without departing from the spirit or scope of the invention, as expressed in the following claims:

What I claim is:

l. Ina power unit comprising a plurality of opposed-piston engines each having, a group of parallel cylinders, a pair of opposed pistons reciprocating in each of said cylinders, and two engine shafts in axial alignment each of said shafts being actuated by the totality of pistons located in corresponding ends of said cylinders, a power take-off shaft positioned parallel to said engine shafts and arranged to be driven by the totality of the engine shafts located'at corresponding ends of said engines.

2. In a power unit comprising a plurality of two-stroke internal combustion engines, having parallel cylinders, pistons reciprocating in said cylinders, an engine shaft for each engine actuated by the pistons of said engine and parallel to said cylinders, individual frames for said engines containing said cylinders and attached together throughout the length of said cylinders so as to form a scavenge air chamber common to all the cylinders of the unit and enclose a power take-off shaft positioned parallel to and actuated by the said engine shafts.

3. In a power unit comprising a plurality of two-stroke internal combustion engines, having parallel cylinders, pistons reciprocating in said cylinders, an engine shaft for each engine actuated by the pistons of said engine and parallel to said cylinders, individual frames for said engines containing said cylinders and attached together throughout the length of said cylinders so as to form an exhaust chamber common to all the cylinders of the unit and enclose a power take-01f shaft positioned parallel to and actuated by the said engine shafts.

4. In a power unit comprising a plurality of two-stroke internal combustion engines, having parallel cylinders, pistons reciprocating in said cylinders, an engine shaft for each engine actuated by the pistons of said engine and parallel to said cylinders, individual frames for said engines containing said cylinders and attached together throughout the length of said cylinders so as to form a chamber for circulation of cooling fluid common to all the cylinders of the unit and enclose a power take-off shaft positioned parallel to and actuated by the said engine shafts.

5. In a power unit comprising a plurality of two-stroke internal combustion engines, having parallel cylinders, pistons reciprocating in said cylinders, an engine shaft for each engine actuated by the pistons of said engine and parallel to said cylinders, individual frames for said engines containing said cylinders and attached together throughout the length of said cylinders so' as to form exhaust and scavenge-air chambers common to all the cylinders of the unit and enclose a power take-off shaft positioned parallel to and actuated by the said engine shafts.

ANTHONY GEORGE MALDON MICHEIL. 

